Scientists Uncover Ancient Salt Deposits on Asteroid Ryugu – Was There Water?

Scitech Daily ^ | February 19, 2025 | Kyoto University

[Red Badger]

Colorized microscopic image of sodium carbonate deposit on Ryugu sample. Credit: KyotoU/Toru Matsumoto

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Deposits Found on a Nearby Asteroid Point to Salty Water in the Outer Solar System

Scientists have uncovered salt minerals in samples from asteroid Ryugu, pointing to a past with liquid water. The presence of these salts suggests that Ryugu’s parent body once hosted a warm, saline environment before the water vanished. This discovery could help us understand the role of water in shaping planets and moons across the Solar System.

Ryugu’s Salty Secret: What Scientists Found

Asteroids that pass near Earth often spark concern about potential collisions, no matter how unlikely. However, their proximity also presents valuable opportunities to study the universe. One such asteroid, Ryugu, measuring about 900 meters across and part of the Apollo group, has recently provided new insights into the search for life’s building blocks beyond Earth.

Researchers from Kyoto University have discovered salt minerals in samples collected from Ryugu during Japan’s Hayabusa2 mission. These deposits, which include sodium carbonate, halite, and sodium sulfates, suggest that liquid saltwater once existed within Ryugu’s parent body.

Preserving Clues from Space

Before analyzing the samples, scientists suspected that Ryugu might contain compounds not typically found in meteorites. They anticipated the presence of highly water-soluble materials that would react quickly with Earth’s moisture, making them difficult to detect unless studied in their original, space-preserved state.

“Careful handling allowed us to identify the delicate salt minerals, providing a unique glimpse into Ryugu’s chemical history,” says corresponding researcher Toru Matsumoto.

Ryugu’s Past: A Watery Beginning?

Experts believe the asteroid was once part of a larger parent body that existed about 4.5 billion years ago, shortly after the formation of the solar system. This parent body would have been heated by radioactive decay, creating an environment of hot water below 100°C. While Ryugu and its grains did not contain any moisture, questions remain about how the liquid water was lost.

The Vanishing Act: How Did Water Disappear?

“These crystals tell us how liquid water disappeared from Ryugu’s parent body,” says Matsumoto. The salt crystals dissolve easily in water, suggesting that they could only have precipitated within highly saline water and in conditions with a limited amount of liquid.

“We hypothesized that as fractures exposed the saltwater to space or as the parent body cooled, this liquid could have either evaporated or frozen,” Matsumoto explains. “The salt minerals we’ve found are the crystallized remnants of that water.”

Comparing Ryugu to Other Icy Worlds

The deposits could prove crucial in comparing the evolved water in the dwarf planet Ceres – located in the Asteroid Belt – and the moons of Jupiter and Saturn, since researchers believe these icy bodies harbor subsurface oceans or liquid reservoirs. They expect sodium carbonates and halite will be found in surface deposits on Ceres, in water plumes from Saturn’s satellite Enceladus, and on the surfaces of Jupiter’s satellites Europa and Ganymede.

A New Key to Planetary Evolution

Since salt production is closely linked to the geological settings and brine chemistry in these aqueous bodies, the discovery of sodium salts in the Ryugu samples provide new insights for comparing the role that water has played in the development of planets and moons in the outer Solar System.

Reference:

“Sodium carbonates on Ryugu as evidence of highly saline water in the outer Solar System”

by Toru Matsumoto, Takaaki Noguchi, Akira Miyake, Yohei Igami, Megumi Matsumoto, Toru Yada, Masayuki Uesugi, Masahiro Yasutake, Kentaro Uesugi, Akihisa Takeuchi, Hayato Yuzawa, Takuji Ohigashi and Tohru Araki, 18 November 2024, Nature Astronomy.

DOI: 10.1038/s41550-024-02418-1

[SunkenCiv]

Thanks Red Badger.

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[null and void]

When did our Sun go nova and spit out a bunch of rocks? I’ve never heard about this.

There's a solar micronova about every 12,000 years.

12,000 Year Cycle

[telescope115]

Makes me wonder about Jupiter’s moon, Io. I wonder if they’ll find salt in the sea under the fractured surface ice there.

[Red Badger]

Almost inevitable.

Water is the ‘universal solvent’. Even ‘freshwater’ has some salts in it...........